Structure of Dark Matter in Galaxies
| Main Author: | Trott, Cathryn Margaret |
|---|---|
| Format: | info publication-thesis Journal |
| Terbitan: |
, 2004
|
| Online Access: |
https://zenodo.org/record/2545058 |
Daftar Isi:
- The origin, nature and distribution of dark matter in the universe form some of the biggest questions in modern astrophysics. Dark matter is distributed on a wide range of scales in the universe. This thesis concentrates on galactic scales, attempting to lower the veil and probe the structure of dark matter in galaxies. The mass distribution of the lensing galaxy 2237+0305 is studied and a combination of photometric, lensing and kinematic data used to constrain the contribution of the luminous and dark mass components to the system. The galaxy is best- tted with a softened isothermal-like halo (inner logarithmic slope 0, outer slope {2.5), and a sub-maximal disk. The kinematic model requires further improvement for this result to be rigorous, however the density profiles produced in N-body simulations are not preferred over a halo with a constant density core (r ~ 1 kpc). The results suggest that the combination of lensing, kinematic and photometric data provides the strongest constraints on the distribution of dark matter in galaxies. Subhalos of dark matter, orbiting within the potential of our Galaxy, will interact gravitationally with the stars in the disk if they pass within their region of influence. Subhalos can be detected by signatures in the phasespace distribution of the stellar disk. Such signatures and their magnitudes are calculated for subhalos with mass and distribution expected from N-body simulations. The capabilities of the ESA satellite GAIA are used as the potential detection thresholds. Uncertainties in the distances to stars combined with the expected steep mass function of dark matter subhalos and the rareness of their passage through the stellar disk, make their detection unlikely with the GAIA satellite. The statistical mechanics of self-gravitating systems provide interesting insights into their behaviour. A spherically symmetric, static dark matter halo is studied using a statistical mechanical approach. The gravitational potential is artificially softened to mimic the conditions under which N-body simulations are performed, and the behaviour of the system compared with that for a purely gravitational potential. The system exhibits a low temperature phase, not accessible with pure gravity, which exists at energies probed by many simulations. Consequently, there is no obvious reason to expect agreement between simulated and observed profiles unless the gravitational potential is appreciably softened in nature.